Casus 1:

You make an ECG (10 mm/mV, 25 mm/sec) in a 16-yr old MN cat. On physical examination the cat is BAR and the pulse rate is 120 beats per minute.

What is your ECG diagnosis?

  1. Ventricular tachycardia
  2. Sinus rhythm
  3. Second degree AV-block
  4. Atrial fibrillation
  5. Atrial standstill

Answer: the rhythm is a sinus rhythm. Although the complexes in lead I are very small, in lead II and III an interpretation is quite straightforward. P-QRS-T-complexes are regular. Therefore, the rhythm is a (normal) sinusrhythm. It is important to realize that QRS-complexes in cats are typically of low amplitude compared with dogs.

 

Casus 2:

You make an ECG (10 mm/mV, 25 mm/sec) in a 12-yr old MN cat. On physical examination the cat is BAR and the pulse rate is 140 beats per minute. You note that the pulse rate is irregular. This is confirmed on cardiac auscultation.

What is your ECG diagnosis?

  1. Normal sinus rhythm
  2. Normal sinus rhythm with ventricular premature complexes (VPCs)
  3. Normal sinus rhythm with supraventricular premature complexes
  4. Atrial fibrillation
  5. Intermittent AV-block

Answer: the basic rhythm is a sinus rhythm. Although the complexes in lead I again are very small, in lead II and III an interpretation is quite straightforward.

P-QRS-T-complexes are however irregular, this is always abnormal in cats. The 5th and 6th complexes are normal sinusnode-generated cardiac depolarization. The 7th depolarization is premature, with a ‘negative’p-wave, but a normal QRS-complex. This is also the case for the 8th, 9th, 10th, and 11th depolarization. The 12th complex is a normal sinus node generated beat again. The abnormal beats are the premature ones, and the abnormal p-wave configuration tells us that the depolarization is originating from somewhere supraventricular (atrial most likely).

Therefore the correct answer is 3. An echocardiogram is recommended to further assess atrial function and size. Most likely one or both atria are enlarged, secondary to ventricular dysfunction. Isolated atrial or ventricular premature complexes are usually not treated.

 

Casus 3:

You make an ECG (10 mm/mV, 25 mm/sec) in a 16-yr old FN cat. On physical examination the cat is BAR and the pulse rate is 140 beats per minute. You note that the pulse rate is irregular. This is confirmed on cardiac auscultation.

 

What is your ECG diagnosis?

  1. Sinus rhythm with ventricular premature complexes
  2. Atrial fibrillation
  3. Ventricular tachycardia
  4. Second degree AV-block
  5. Sinus rhythm

Answer: the basic rhythm is a sinus rhythm. The first four depolarisations are normal. A 5th P-wave can be seen, but this is NOT followed by a QRS-complex. After about 10 mm (0.4sec) an abnormal complex (wide, bizarre, mainly negative in all leads) can be seen. This complex is of ventricular origin. Because it occurs after a longer pause it is NOT a VPC, but a ventricular escape beat. The 6th complex is normal again, followed by failure of conduction of a p-wave with a ventricular escape beat. This rhythm repeats itself more or less. The 11th complex is also a ventricular escape beat, and just before that beat another p-wave is seen. The PQ-time is really short.

The diagnosis therefore is second degree AV-block. An echocardiogram is recommended to further cardiac function. An atropine response test is recommended to assess for high vagal tone. A cardiac work-up is needed to assess underlying causes. Pacemaker therapy is indicated if the cat would be symptomatic.